Giant spin and orbital moment anisotropies of a Cu-phthalocyanine monolayer

The magnetism of a Cu-phthalocyanine (CuPc) monolayer on Ag(100) was investigated using x-ray magnetic circular dichroism (XMCD) and ligand-field multiplet calculations. Contrary to other metal-Pc adsorbed on metals, we show that the local CuPc moment survives the interaction with the electronic states of the substrate and presents enhanced susceptibility with respect to bulk powder samples. Our measurements reveal extraordinary orbital moment anisotropy (500%) and an anisotropic spin dipole moment up to twice the isotropic spin in a metal-organic layer. A complete description of the orbital, spin, and spin-orbit operators is provided based on the XMCD sum rules.